Simple math for better mornings.

Sleep Calculator AI is a free tool built on a single idea: when you wake up matters almost as much as how long you sleep. Sleep moves in cycles of roughly 90 minutes, and an alarm that lands mid-cycle is what makes mornings feel heavy.

Our calculators do one job well — they work backwards (or forwards) from your time in bed, add a 15-minute window to fall asleep, and suggest times that line up with the end of a sleep cycle. No accounts, no tracking, no paywall.

The guidance on this site is educational. It is based on widely accepted sleep science, but it is not medical advice — if you suspect a sleep disorder, please talk to a qualified health professional.